This invention relates to rotary carburizing furnaces utilizing a high carbon-potential atmosphere contained within the furnace by oil seals, and particularly to purging the high carbon-potential atmosphere from the vicinity of the oil seals, and to providing a cooling and recirculating management system for the seal oil.
In rotary carburizing furnaces, metal parts are carburized by exposing them to a high carbon-potential, high temperature furnace atmosphere. Typically, the furnace atmosphere is an endothermic carrier gas carbon enriched with a hydrocarbon gas such as methane. While the furnace atmosphere will support gaseous carbon at high temperatures, carbon will precipitate out of the furnace atmosphere if the temperature of the atmosphere drops below the saturation point. Carbon precipitation often occurs in the vicinity of the oil seal or seals of a rotary carburizing furnace since these seals are in contact with the carbon-enriched furnace atmosphere, and are located at a cooler section of the furnace chamber, e.g., below the rotating hearth. Carbon precipitation is exacerbated particularly when the furnace atmosphere is close to carbon saturation, which may be desirable for the carburizing cycle, since only a small temperature decrease is required to cause precipitation.
Carbon precipitation in the vicinity of furnace oil seals causes carbon sludge to form in the seal oil, causing the oil seal to clog quickly. Since seal oil is typically recirculated and cooled to prevent overheating, carbon clogging of the oil seal, and of the recirculation and cooling system, must be prevented. Clogging of the oil seal system can also cause oil overflows onto the plant floor. Mechanical, manual cleaning of the oil seals to prevent or remove clogging requires a costly shutdown of the rotary carburizing furnace and lost production capacity.
Accordingly, it is an object of the invention to provide a method and apparatus for avoiding or minimizing entry of carbon into a fluid seal.
It is a particular object of this invention to minimize or eliminate carbon precipitation in the vicinity of one or more oil seals of a rotary carburizing furnace.
It is another object of this invention to provide an oil seal management system for cooling, cleaning and recirculating oil through the oil seals.